1. Field of the Invention
The present invention relates to an image-forming device such as a laser printer, and to a process cartridge detachably provided in the image-forming device.
2. Description of the Related Art
Generally, laser printers and other electrophotographic image-forming devices are provided with a photosensitive drum for carrying a developer image, and a transfer roller disposed in contact with the photosensitive drum for attracting the developer image with a transfer bias applied to the transfer roller. When a sheet of paper passes between the photosensitive drum and the transfer roller, the developer image migrates toward the transfer roller and is transferred onto the paper, forming an image thereon. However, when the paper is separated from the photosensitive drum at a position upstream of a transfer position between the photosensitive drum and the transfer roller with respect to the paper-conveying direction, a pre-transfer may occur in which an electric field produced between the paper and the photosensitive drum causes developer to scatter from the photosensitive drum onto the paper.
To resolve this problem, a guide plate has conventionally been provided on the upstream side of the transfer position for guiding the paper toward the photosensitive drum in order to suppress pre-transfer. This technology is disclosed in Japanese unexamined patent application publication No. 2003-5535 (FIG. 1).
However, when the trailing edge (upstream end) of the paper passes over the edge of the guide plate in the technology described above, the trailing edge supported on the guide plate to that point becomes free and flaps. Flapping in the trailing edge of the paper can cause problems in transferring the developer, leading to a reduced quality in the image formed on the paper.